I've been meaning to ask this for a while; the growing stain on the street
in front of my house makes me get it in gear. My '83 diesel Vanagon has a
unique (in my experience) oil drain plug. The sealing surface is
hemispherical, and it sits horizontally on the oil pan. Hard to describe,
but...mine has always leaked. I replaced the drain plug once - no change.
Has anyone dealt with this, or has anyone got any ideas on a fix?  Thanks,
David